1. Field of the Invention
The invention relates to an arrangement for current limiting, using components composed of a superconducting material which are arranged in a cryostat which comprises two metallic tubes which are arranged concentrically with respect to one another and between which vacuum insulation is fitted, and which cryostat surrounds a free space for a coolant to pass through (EP 1 681 731 A1).
2. Description of Related Art
By way of example, superconducting materials are used as conductors in cables which are used for electrical power transmission. In modern technology, the superconducting material comprises a composite material which contains ceramic material, which changes to the superconducting state at sufficiently low temperatures. The electrical direct-current resistance of a conductor constructed in this way is zero if the cooling is adequate, provided that a specific current level, the critical current level, is not exceeded. By way of example, suitable ceramic materials are oxidic materials based on rare earths (ReBCO), in particular YBCO (yttrium-barium-copper oxide), or BSCCO (bismuth-strontium-calcium-copper oxide). By way of example, sufficiently low temperatures to change such a material to the superconducting state are between 67 K and 110 K. By way of example, suitable coolants are nitrogen, helium, neon and hydrogen or mixtures of these substances.
An arrangement fore current limiting, as described initially, can be installed as a type of fuse in any desired transmission path, such as a cable path or else a switchgear assembly, via which or in which currents of greater or lesser magnitude are transmitted. The aim is to prevent considerable damage occurring to the transmission path to be protected, in the event of a short circuit acting on the latter. In the event of a short circuit, the electrical impedance of the arrangement rises considerably in such a way that this itself greatly reduces the peak short-circuit current. The transmission path can then be interrupted by a circuit breaker in order to overcome the short circuit. Once the cause of the short circuit has been rectified, the transmission path can be reconnected without any need to make any changes to the current-limiting arrangement.
The initially cited EP 1 681 731 A1 describes an arrangement having at least one superconducting component for current limiting. The component comprises a cylindrical support composed of superconducting material around which a superconducting conductor is wound, with a normal conductor connected in parallel with it. A plurality of such components are arranged connected electrically in series or in parallel in order to produce a current limiter.